Radiotherapy promotes tumor-specific effector CD8+ T cells via dendritic cell activation

Complement is a central mediator of radiotherapy-induced tumor-specific immunity and clinical response

Radiotherapy induces DNA damage and cell death, but recent data suggest that concomitant immune stimulation is an integral part of the therapeutic action of ionizing radiation. It is poorly understood how radiotherapy supports tumor-specific immunity. Here we report that radiotherapy induced tumor cell death and transiently activated complement both in murine and human tumors. The local production of pro-inflammatory anaphylatoxins C3a and C5a was crucial to the tumor response to radiotherapy and concomitant stimulation of tumor-specific immunity. Dexamethasone, a drug frequently given during radiotherapy, limited complement activation and the anti-tumor effects of the immune system. Overall, our findings indicate that anaphylatoxins are key players in radiotherapy-induced tumor-specific immunity and the ensuing clinical responses.

Kill and spread the word: stimulation of antitumor immune responses in the context of radiotherapy

Besides the direct, targeted effects of ionizing irradiation (x-ray) on cancer cells, namely DNA damage and cell death induction, indirect, nontargeted ones exist, which are mediated in large part by the immune system. Immunogenic forms of tumor cell death induced by x-ray, including immune modulating danger signals like the heat shock protein 70, adenosine triphosphate, and high-mobility group box 1 protein are presented. Further, antitumor effects exerted by cells of the innate (natural killer cells) as well as adaptive immune system (T cells activated by dendritic cells) are outlined. Tumor cell death inhibiting molecules such as survivin are introduced as suitable target for molecularly tailored therapies in combination with x-ray. Finally, reasonable combinations of immune therapies with radiotherapy are discussed.

Radiation meets immunotherapy - a perfect match in the era of combination therapy?

PURPOSE

This review focuses on recent advances in the field of combining radiation with immunotherapy for the treatment of malignant diseases, since various combinatorial cancer therapy approaches have lately proven highly successful.

RESULTS

With initial case reports and anecdotes progressively converting into solid clinical data, interest in cancer immunotherapy (CIT) has risen steeply. Especially immune checkpoint blockade therapies have recently celebrated tremendous successes in the treatment of severe malignancies resistant to conventional treatment strategies. Nevertheless, the high variability of patient responses to CIT remains a major hurdle, clearly indicating an urgent need for improvement. It has been suggested that successful cancer therapy most probably involves combinatorial treatment approaches. Radiotherapy (RT) has been proposed as a powerful partner for CIT due to its broad spectrum of immune modulatory characteristics. Several preclinical studies, supported by an increasing number of clinical observations, have demonstrated synergistic interactions between RT and CIT resulting in significantly improved therapy outcomes.

CONCLUSIONS

Numerous reports have shown that radiation is capable of tipping the scales from tumor immune evasion to elimination in different tumor types. The next puzzle to be solved is the question of logistics - including types, schedule and dosage of combinatorial RT and CIT strategies.

Prediction of the preoperative chemoradiotherapy response for rectal cancer by peripheral blood lymphocyte subsets

BACKGROUND

Although neoadjuvant chemoradiotherapy (CRT) has become a standard procedure to downstage locally advanced rectal cancer prior to surgery, markers to predict the response to CRT have not been fully identified. The aim of this study was to identify predictive factors of response to CRT, especially focusing on peripheral blood leukocyte subsets.

METHODS

A total of 45 consecutive patients diagnosed with primary rectal cancer were prospectively enrolled and received CRT followed by curative resection. The numbers of each lymphocyte subset in peripheral blood pre- and post-CRT were analyzed using flow cytometry. According to the pathological response to CRT, patients were classified into high (Hi-R) and low (Lo-R) response groups.

RESULTS

Hi-R cases had significantly higher numbers of pre-CRT lymphocytes (p = 0.018), T lymphocytes (p = 0.009) and helper T lymphocytes (Th lymphocytes, p = 0.015) compared to the Lo-R cases. With the receiver-operating characteristic curve for numbers of pre-CRT T lymphocytes, the area under the curve (AUC) was 0.733, and the optimal cutoff value was 1196/μl, with 76.5% sensitivity, 67.8% specificity, 59.1% positive and 82.6% negative predictive values. The numbers of pre-CRT Th lymphocytes and cytotoxic lymphocytes were both independent predictors of the high CRT response in the multivariate analysis.

CONCLUSIONS

In addition to the direct cytotoxicity of CRT, recent studies have demonstrated the induction of an immunological host response, which also contributed to the tumor regression induced by CRT. Our result suggested the potential role of circulating T lymphocytes in predicting the response to CRT in colorectal cancer patients.

Stereotactic Radiation Therapy Augments Antigen-Specific PD-1-Mediated Antitumor Immune Responses via Cross-Presentation of Tumor Antigen

The immune-modulating effects of radiotherapy (XRT) have gained considerable interest recently, and there have been multiple reports of synergy between XRT and immunotherapy. However, additional preclinical studies are needed to demonstrate the antigen-specific nature of radiation-induced immune responses and elucidate potential mechanisms of synergy with immunotherapy. Here, we demonstrate the ability of stereotactic XRT to induce endogenous antigen-specific immune responses when it is combined with anti-PD-1 checkpoint blockade immunotherapy. Using the small animal radiation research platform (SARRP), image-guided stereotactic XRT delivered to B16-OVA melanoma or 4T1-HA breast carcinoma tumors resulted in the development of antigen-specific T cell- and B cell-mediated immune responses. These immune-stimulating effects of XRT were significantly increased when XRT was combined with either anti-PD-1 therapy or regulatory T cell (Treg) depletion, resulting in improved local tumor control. Phenotypic analyses of antigen-specific CD8 T cells revealed that XRT increased the percentage of antigen-experienced T cells and effector memory T cells. Mechanistically, we found that XRT upregulates tumor-associated antigen-MHC complexes, enhances antigen cross-presentation in the draining lymph node, and increases T-cell infiltration into tumors. These findings demonstrate the ability of XRT to prime an endogenous antigen-specific immune response and provide an additional mechanistic rationale for combining radiation with PD-1 blockade in the clinic.

A novel systemically administered Toll-like receptor 7 agonist potentiates the effect of ionizing radiation in murine solid tumor models

Although topical TLR7 therapies such as imiquimod have proved successful in the treatment of dermatological malignancy, systemic delivery may be required for optimal immunotherapy of nondermatological tumors. We report that intravenous delivery of the novel small molecule TLR7 agonist, DSR-6434, leads to the induction of type 1 interferon and activation of T and B lymphocytes, NK and NKT cells. Our data demonstrate that systemic administration of DSR-6434 enhances the efficacy of ionizing radiation (IR) and leads to improved survival in mice bearing either CT26 or KHT tumors. Of the CT26 tumor-bearing mice that received combined therapy, 55% experienced complete tumor resolution. Our data reveal that these long-term surviving mice have a significantly greater frequency of tumor antigen specific CD8(+) T cells when compared to age-matched tumor-naïve cells. To evaluate therapeutic effects on spontaneous metastases, we showed that combination of DSR-6434 with local IR of the primary tumor significantly reduced metastatic burden in the lung, when compared to time-matched cohorts treated with IR alone. The data demonstrate that systemic administration of the novel TLR7 agonist DSR-6434 in combination with IR primes an antitumor CD8(+) T-cell response leading to improved survival in syngeneic models of colorectal carcinoma and fibrosarcoma. Importantly, efficacy extends to sites outside of the field of irradiation, reducing metastatic load. Clinical evaluation of systemic TLR7 therapy in combination with IR for the treatment of solid malignancy is warranted.

Whole-body irradiation increases the magnitude and persistence of adoptively transferred T cells associated with tumor regression in a mouse model of prostate cancer

Adoptive immunotherapy has demonstrated efficacy in a subset of clinical and preclinical studies, but the T cells used for therapy often are rendered rapidly nonfunctional in tumor-bearing hosts. Recent evidence indicates that prostate cancer can be susceptible to immunotherapy, but most studies using autochthonous tumor models demonstrate only short-lived T-cell responses in the tolerogenic prostate microenvironment. Here, we assessed the efficacy of sublethal whole-body irradiation (WBI) to enhance the magnitude and duration of adoptively transferred CD8(+) T cells in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. We demonstrate that WBI promoted high-level accumulation of granzyme B (GzB, Gzmb)-expressing donor T cells both in lymphoid organs and in the prostate of TRAMP mice. Donor T cells remained responsive to vaccination in irradiated recipients, but a single round of WBI-enhanced adoptive immunotherapy failed to affect significantly the existing disease. Addition of a second round of immunotherapy promoted regression of established disease in half of the treated mice, with no progression observed. Regression was associated with long-term persistence of effector/memory phenotype CD8(+) donor cells. Administration of the second round of adoptive immunotherapy led to reacquisition of GzB expression by persistent T cells from the first transfer. These results indicate that WBI conditioning amplifies tumor-specific T cells in the TRAMP prostate and lymphoid tissue, and suggest that the initial treatment alters the tolerogenic microenvironment to increase antitumor activity by a second wave of donor cells.

Radiation as an immune modulator

Radiation therapy is currently one of the most widely utilized treatment strategies in the clinical management of cancer. Classically, radiation therapy was developed as an anticancer treatment on the basis of its capacity to induce DNA double strand breaks in exposed cancer cells, ultimately resulting in tumor cell death. Recently, our understanding of radiation effects has expanded widely in terms of the consequences of radiation-induced tumor cell death and the pertinent cells, signaling pathways, and molecular sensors that modify the tumor response to radiation. It is now well accepted that inflammation plays a complex dual role in promoting or inhibiting tumor growth. The capacity of inflammatory responses to alter the tumor response to radiation therapy, and vice versa, is now the subject of intense scientific and clinical investigation. Herein, we review the concepts regarding the immunostimulatory properties of radiation therapy with particular focus on the effects of radiation therapy on the tumor microenvironment.

Release of monocyte migration signals by breast cancer cell lines after ablative and fractionated γ-irradiation

Background

Radiotherapy, administered in fractionated as well as ablative settings, is an essential treatment component for breast cancer. Besides the direct tumor cell death inducing effects, there is growing evidence that immune mechanisms contribute - at least in part - to its therapeutic success. The present study was designed to characterize the type and the extent of cell death induced by fractionated and ablative radiotherapy as well as its impact on the release of monocyte migration stimulating factors by dying breast cancer cells.

Methods

Cell death and senescence assays were employed to characterize the response of a panel of breast cancer cell lines with different receptor and p53 status towards γ-irradiation applied in a fractionated (daily doses of 2 Gy) or ablative setting (single dose of 20 Gy). Cell-free culture supernatants were examined for their monocyte migration stimulating potential in transwell migration and 2D chemotaxis/chemokinesis assays. Irradiation-induced transcriptional responses were analyzed by qRT-PCR, and CD39 surface expression was measured by flow cytometry.

Results

Fast proliferating, hormone receptor negative breast cancer cell lines with defective p53 predominantly underwent primary necrosis in response to γ-irradiation when applied at a single, ablative dose of 20 Gy, whereas hormone receptor positive, p53 wildtype cells revealed a combination of apoptosis, primary, and secondary (post-apoptotic) necrosis. During necrosis the dying tumor cells released apyrase-sensitive nucleotides, which effectively stimulated monocyte migration and chemokinesis. In hormone receptor positive cells with functional p53 this was hampered by irradiation-induced surface expression of the ectonucleotidase CD39.

Conclusions

Our study shows that ablative radiotherapy potently induces necrosis in fast proliferating, hormone receptor negative breast cancer cell lines with mutant p53, which in turn release monocyte migration and chemokinesis stimulating nucleotides. Future studies have to elucidate, whether these mechanisms might be utilized in order to stimulate intra-tumoral monocyte recruitment and subsequent priming of adaptive anti-tumor immune responses, and which breast cancer subtypes might be best suited for such approaches.

Enhancement of T cell responses as a result of synergy between lower doses of radiation and T cell stimulation

As a side effect of cancer radiotherapy, immune cells receive varying doses of radiation. Whereas high doses of radiation (>10 Gy) can lead to lymphopenia, lower radiation doses (2-4 Gy) represent a valid treatment option in some hematological cancers, triggering clinically relevant immunological changes. Based on our earlier observations, we hypothesized that lower radiation doses have a direct positive effect on T cells. In this study, we show that 0.6-2.4 Gy radiation enhances proliferation and IFN-γ production of PBMC or purified T cells induced by stimulation via the TCR. Radiation with 1.2 Gy also lowered T cell activation threshold and broadened the Th1 cytokine profile. Although radiation alone did not activate T cells, when followed by TCR stimulation, ERK1/2 and Akt phosphorylation increased above that induced by stimulation alone. These changes were followed by an early increase in glucose uptake. Naive (CD45RA(+)) or memory (CD45RA(-)) T cell responses to stimulation were boosted at similar rates by radiation. Whereas increased Ag-specific cytotoxic activity of a CD8(+) T cell line manifested in a 4-h assay (10-20% increase), highly significant (5- to 10-fold) differences in cytokine production were detected in 6-d Ag-stimulation assays of PBMC, probably as a net outcome of death of nonstimulated and enhanced response of Ag-stimulated T cells. T cells from patients receiving pelvic radiation (2.2-2.75 Gy) also displayed increased cytokine production when stimulated in vitro. We report in this study enhanced T cell function induced by synergistic radiation treatment, with potential physiological significance in a wide range of T cell responses.

Norm- and hypo-fractionated radiotherapy is capable of activating human dendritic cells

Despite the transient immunosuppressive properties of local radiotherapy (RT), this classical treatment modality of solid tumors is capable of inducing immunostimulatory forms of tumor-cell death. The resulting 'immunotoxicity' in the tumor, but not in healthy tissues, may finally lead to immune-mediated destruction of the tumor. However, little is known about the best irradiation scheme in this setting. This study examines the immunological effects of differently irradiated human colorectal tumor cells on human monocyte-derived dendritic cells (DC). Human SW480 tumor cells were irradiated with a norm-fractionation scheme (5 × 2 Gy), a hypo-fractionated protocol (3 × 5 Gy), and with a high single irradiation dose (radiosurgery; 1 × 15 Gy). Subsequently, human immature DC (iDC) were co-incubated with supernatants (SN) of these differently treated tumor cells. Afterwards, DC were analyzed regarding the expression of maturation markers, the release of cytokines, and the potential to stimulate CD4(+) T-cells. The co-incubation of iDC with SN of tumor cells exposed to norm- or hypo-fractionated RT resulted in a significantly increased secretion of the immune activating cytokines IL-12p70, IL-8, IL-6, and TNFα, compared to iDC co-incubated with SN of tumor cells that received a high single irradiation dose or were not irradiated. In addition, DC-maturation markers CD80, CD83, and CD25 were also exclusively elevated after co-incubation with the SN of fractionated irradiated tumor cells. Furthermore, the SN of tumor cells that were irradiated with norm- or hypo-fractionated RT triggered iDC to stimulate CD4(+) T-cells not only in an allogenic, but also in an antigen-specific manner like mature DC. Collectively, these results demonstrate that norm- and hypo-fractionated RT induces a fast human colorectal tumor-cell death with immunogenic potential that can trigger DC maturation and activation in vitro. Such findings may contribute to the improvement of irradiation protocols for the most beneficial induction of anti-tumor immunity.

Hypericin-based Photodynamic Therapy Induces a Tumor-Specific Immune Response and an Effective DC-based cancer Immunotherapy

In our study, we find that photodynamic therapy (PDT), which generates reactive oxygen species (ROS) -mediated endoplasmic reticulum (ER) stress to inflict trauma in the targeted lesion, can break the balance between membrane damage-associated molecular patterns (DAMPs) and integrin-associated protein (CD47). The imbalance undermines the ability of lewis lung carcinoma (LLC) cells to escape immune attack by increasing the uptake of hypericin-mediated PDT(hyp-PDT) killed lewis lung carcinoma (LLC) cells by homologous dendritic cells (DCs), accompanied by phenotypic maturation (CD80high, CD86high, and CD40high) and functional stimulation (NOhigh, IL-10absent) of dendritic cells as well as subsequent T-cell response. Besides, C57BL/6 mice vaccinated with dendritic cells (DCs) pulsed with PDT-treated LLCs (PDT-DCs) or PDT-treated LLCs alone (PDT-LLCs) show potent immunity against LLC tumor. These data identify hypericin-induced PDT as a strong inducer of immunogenic apoptosis, providing an antitumor vaccination strategy for personalized cancer Immunotherapy.

Long-term complete remission following radiosurgery and immunotherapy in a melanoma patient with brain metastasis: immunologic correlates

A melanoma patient with brain metastases was treated by gamma-knife radiosurgery and immunotherapy with autologous tumor-lysate-loaded dendritic cells (DC). Ten years after the combined treatment, the patient remains in complete remission. Remarkable immunologic correlates to the clinical development were the transient induction of NY-ESO-1 antibody and the durable expansion of MAGE-A1p161-169 EADPTGHSY-specific CD8+ T cells. Although the induction of NY-ESO-1 antibody most likely resulted from gamma-knife-mediated "auto-vaccination," the persistence of circulating MAGE-A1-specific T cells, which are still detectable ex vivo in the absence of any tumor manifestation, coincides with DC-based vaccination administered monthly until today.

Nanosecond pulsed electric field (nsPEF) treatment for hepatocellular carcinoma: a novel locoregional ablation decreasing lung metastasis

Hepatocellular carcinoma (HCC) is a highly aggressive malignancy. Nanosecond pulsed electric field (nsPEF) is a new technology destroying tumor cells with a non-thermal high voltage electric field using ultra-short pulses. The study's aim was to evaluate the ablation efficacy of nsPEFs with human HCC cell lines and a highly metastatic potential HCC xenograft model on BALB/c nude mice. The in vivo study showed nsPEFs induced HCC cell death in a dose dependent manner. On the high metastatic hepatocellular carcinoma cell line (HCCLM3) xenograft mice model, tumor growth was inhibited significantly in nsPEF-treated- groups (single dose and multi-fractionated dose). Besides a local effect, the nsPEF treatment reduced pulmonary metastases. The nsPEFs also enhanced HCC cell phagocytosis by human macrophage cell (THP1) in vitro. The nsPEF is efficient in controlling HCC progression and reducing its metastasis. NsPEF treatment may elicit a host immune response against tumor cells. This study suggests nsPEF therapy could be used as a potential locoregional therapy for hepatocellular carcinoma.

Radiotherapy and the tumor stroma: the importance of dose and fractionation

Ionizing radiation is a non-specific but highly effective way to kill malignant cells. However, tumor recurrence sustained by a minor fraction of surviving tumor cells is a commonplace phenomenon caused by the activation of both cancer cell intrinsic resistance mechanisms, and also extrinsic intermediaries of therapy resistance, represented by non-malignant cells and structural components of the tumor stroma. The improved accuracy offered by advanced radiotherapy (RT)-technology permits reduced volume of healthy tissue in the irradiated field, and has been triggering an increase in the prescription of high-dose oligo-fractionated regimens in the clinics. Given the remarkable clinical success of high-dose RT and the current therapeutic shift occurring in the field, in this review we revise the existing knowledge on the effects that different radiation regimens exert on the different compartments of the tumor microenvironment, and highlight the importance of anti-tumor immunity and other tumor cell extrinsic mechanisms influencing therapeutic responses to high-dose radiation.

Antitumor immune responses induced by ionizing irradiation and further immune stimulation

The therapy of cancer emerged as multimodal treatment strategy. The major mode of action of locally applied radiotherapy (RT) is the induction of DNA damage that triggers a network of events that finally leads to tumor cell cycle arrest and cell death. Along with this, RT modifies the phenotype of the tumor cells and their microenvironment. Either may contribute to the induction of specific and systemic antitumor immune responses. The latter are boosted when additional immune therapy (IT) is applied at distinct time points during RT. We will focus on therapy-induced necrotic tumor cell death that is immunogenic due to the release of damage-associated molecular patterns. Immune-mediated distant bystander (abscopal) effects of RT when combined with dendritic cell-based IT and the role of fractionation of radiation in the induction of immunogenic tumor cell death will be discussed. Autologous whole-tumor-cell-based vaccines generated by high hydrostatic pressure technology will be introduced and the influence of cytokines and the immune modulator AnnexinA5 on the ex vivo generated or in situ therapy-induced vaccine efficacy will be outlined. RT should be regarded as immune adjuvant for metastatic disease and as a tool for the generation of an in situ vaccine when applied at distinct fractionation doses or especially in combination with IT to generate immune memory against the tumor. To identify the most beneficial combination and chronology of RT with IT is presumably one of the biggest challenges of innovative tumor research and therapies.

Immature, Semi-Mature, and Fully Mature Dendritic Cells: Toward a DC-Cancer Cells Interface That Augments Anticancer Immunity

Dendritic cells (DCs) are the sentinel antigen-presenting cells of the immune system; such that their productive interface with the dying cancer cells is crucial for proper communication of the "non-self" status of cancer cells to the adaptive immune system. Efficiency and the ultimate success of such a communication hinges upon the maturation status of the DCs, attained following their interaction with cancer cells. Immature DCs facilitate tolerance toward cancer cells (observed for many apoptotic inducers) while fully mature DCs can strongly promote anticancer immunity if they secrete the correct combinations of cytokines [observed when DCs interact with cancer cells undergoing immunogenic cell death (ICD)]. However, an intermediate population of DC maturation, called semi-mature DCs exists, which can potentiate either tolerogenicity or pro-tumorigenic responses (as happens in the case of certain chemotherapeutics and agents exerting ambivalent immune reactions). Specific combinations of DC phenotypic markers, DC-derived cytokines/chemokines, dying cancer cell-derived danger signals, and other less characterized entities (e.g., exosomes) can define the nature and evolution of the DC maturation state. In the present review, we discuss these different maturation states of DCs, how they might be attained and which anticancer agents or cell death modalities (e.g., tolerogenic cell death vs. ICD) may regulate these states.

Immune-maximizing (IMAX) therapy for cancer: Combination of dendritic cell vaccine and intensity-modulated radiation

A dendritic cell (DC)-based vaccine was combined with intensity-modulated radiotherapy (IMRT) or other conformal radiotherapy (RT), assuming minimal immunosuppression by such RT modalities. In this study, the outcomes in the first 40 patients are presented. The patients had recurrent, metastatic or locally advanced tumors. Nine had previously undergone full-course RT. Peripheral blood mononuclear cells obtained by leukapheresis were cultured with granulocyte-macrophage colony-stimulating factor, interleukin-4, OK-432 and prostaglandin E2 to generate DCs, which were pulsed with autologous tumor lysates or tumor-specific peptides, such as WT1. IMRT using tomotherapy, stereotactic irradiation or 3-dimensional conformal RT (3DCRT) was initially administered. The standard dose was 30 and 60 Gy in patients with and without previous RT, respectively. Every other week thereafter, up to a total of 7 times, DC vaccines were injected directly into the tumor (n=15) or administered intradermally when DCs were pulsed with tumor lysates or peptides. The tumor response was evaluated according to the response evaluation criteria in solid tumors (RECIST). RT and DC vaccines were well tolerated and there were no major complications. Three patients were not able to complete the planned DC therapy due to disease progression. For the 31 patients receiving full-dose RT, the response rate was 61% and for the 9 patients who had previously received RT, the response rate was 55%. In 9 patients, the tumor response outside the RT target volume was evaluable: 22% had a partial response (PR), 33% had stable disease (SD) and 44% had progressive disease (PD). In conclusion, a combination of IMRT (or 3DCRT) and DC vaccine is feasible and requires further investigation.

Changes in the Secretory Profile of NSCLC-Associated Fibroblasts after Ablative Radiotherapy: Potential Impact on Angiogenesis and Tumor Growth

In the context of radiotherapy, collateral effects of ablative doses of ionizing radiation (AIR) on stromal components of tumors remains understudied. In this work, cancer-associated fibroblasts (CAFs) isolated from freshly resected human lung tumors were exposed to AIR (1x 18 Gy) and analyzed for their release of paracrine factors. Inflammatory mediators and regulators of angiogenesis and tumor growth were analyzed by multiplex protein assays in conditioned medium (CM) from irradiated and non-irradiated CAFs. Additionally, the profile of secreted proteins was examined by proteomics. In functional assays, effects of CAF-CM on proliferative and migratory capacity of lung tumor cells (H-520/H-522) and human umbilical vein endothelial cells (HUVECs) and their tube-forming capacity were assessed. Our data show that exposure of CAFs to AIR results in 1) downregulated release of angiogenic molecules such as stromal cell-derived factor-1, angiopoietin, and thrombospondin-2 (TSP-2); 2) upregulated release of basic fibroblast growth factor from most donors; and 3) unaffected expression levels of hepatocyte growth factor, interleukin-6 (IL-6), IL-8, IL-1β, and tumor necrosis factor-α. CM from irradiated and control CAFs did not affect differently the proliferative or migratory capacity of tumor cells (H-520/H-522), whereas migratory capacity of HUVECs was partially reduced in the presence of irradiated CAF-CM. Overall, we conclude that AIR mediates a transformation on the secretory profile of CAFs that could influence the behavior of other cells in the tumor tissue and hence guide therapeutic outcomes. Downstream consequences of the changes observed in this study merits further investigations.

The confluence of radiotherapy and immunotherapy

Radiotherapy (RT) has been considered a local modality and outcomes have emphasized local and regional control of tumors. Recent data suggests that RT may activate the immune system and the combination of radiation therapy and immune therapies may have the potential to improve both local and distant control of tumor deposits. Below we review principals underlying the concepts of combining both modalities.